The invention relates to a climate controlled cabinet and a method for operating such a cabinet according to the preamble of the independent claims.
In substance research and microbiology the used objects must be stored under exactly predefined climatic conditions. The temperatures of the storage range typically approximately from the freezing point of water up to room temperature. The objects usually consist of containers for several liquid probes. The volumes of the probes are becoming smaller and smaller, and the logistics of the objects are increasingly carried out automatically. The capacity of the storage systems increases and, often, several such storage systems are used within one system. The value of the objects stored in the storage systems is extremely high and can be a multiple of the costs of the whole system. An accidental misidentification between objects must be prevented at any circumstance.
Today, storage systems are offered with integrated handling device for manipulating the objects. In WO98/05753 and U.S. Pat. No. 6,129,428, a climate controlled cabinet with automatic access feature is described. A user door and an automatically operable auxiliary door as well as, within the climate controlled cabinet, a positionable carousel with a handling device are provided. The integrated handling device comprises, necessarily, sensors and driving motors. Both give off heat to the climate controlled chamber. Because of the high insulating values of the cabinet insulation, even small heat sources can lead to substantial inherent warming of the climate controlled chamber and to undesired condensation at the walls, or they even make it impossible to maintain the desired temperature. In this device, the objects can be removed easily and quickly in case of a defect by using storage towers. The storage density per laboratory area in this system is, however, small. Also disadvantageous is the design of the storage towers, which does not allow a secure manual loading and unloading of the objects to be stored, does not have the mechanical precision required for automatic access and can even represent a danger of injury at the sharp edges.
Another apparatus uses shelves for receiving the objects. Such embodiments can, basically, be constructed to be as large as required, but they have the decisive disadvantage that the objects can only be loaded or unloaded manually in complicated manner and at a large risk of misidentification.
In CH 690 645 a climate controlled cabinet with user door and automatically operable auxiliary door is described, wherein fixedly arranged storage towers and a handling device are arranged within it. Such designs are only suited for a small number of storage towers and are therefore not suited for being used in larger systems.
In EP 1 155 743 a transport device with a drive arranged on a scoop and a counter weight is shown. This arrangement is not suited for a large number of accesses. If the substances have to remain within the cabinet for a long time, the transport system should, however, be maintenance free because maintenance work causes a loss of climatization. A further disadvantage of the device according to this publication is that the arrangement of the scoop drive degrades the usage of available space if the scoop mechanism is used in connection with a carousel in a climate controlled cabinet because the horizontal arrangement of the scoop drive requires a large lateral displacement for the cog rail. This, and the length of the motor of the scoop drive require the tapered front and back end of the scoop holder to become larger. For an arrangement of the scoop mechanism in the corner of a climate controlled chamber, as it is usual for carousel systems, this requires the carousel to be moved further away from the corner, which in turn requires the climate controlled chamber to be larger.
A common trait of the above devices is that, apart from the automatic access, they achieve an improvement of climatic stability by means of a small auxiliary door. When access occurs very frequent and at short time intervals, however, undesired climatic fluctuations occur also for these devices. Objects that are removed from the climate controlled chamber require, furthermore, substantial time until they reach the desired storage temperature again. This disadvantage is particularly disturbing because, in storage applications, the same object has often to be removed from the climate controlled chamber and fed back repetitively in short temporal intervals. Furthermore, the known devices cannot satisfy the desire for high access times even for large access paths while being maintenance-free at the same time.
In storage applications, a particular significance has to be attributed to humidity, for two reasons. First, it suffers much more under accesses than, for example, temperature, and, second, it determines the evaporation limited storage duration of the objects in the climate controlled chamber. Maximum humidity—typically for solutions in water—may be desired, as well as accurately defined humidity values, e.g. when using hygroscopic solutions, such as DMSO.
Adding a cooling device is, in the concerned applications, not possible without further measures because cooling is problematic when the humidity is high. For achieving high humidity, incubators of known type comprise insulation plates arranged at a given distance from the incubation chamber and thus form an air coat around the incubation chamber. This results in a homogeneous temperature distribution on the wall of the incubation chamber. If this hollow space were cooled, condensed water would result.
For an insulation suited for cooling, the cavity would have to be filled by foaming. This would, however, cause a loss of the homogenization of the temperature that was achieved by the cavity. Furthermore, foaming would require complicated scaffolding for receiving the forces generated by the foaming process. Finally, a foamed isolation can hardly be opened anymore. This would make maintenance or repair work for components arranged around the climate controlled space impossible or at least difficult. Also, building a scaffolding is expensive. For the small product life times, small numbers of units and large product diversity in the market of automatic incubators, such investments could not be amortised. Commercial standard devices do not have the desired dimensions for the climate controlled chamber. Also, the usual cooling used in such devices, where a cooling member is arranged in the climate controlled chamber or in a extended part of the climate controlled chamber, would lead to a drying out of the climate controlled chamber. This is caused by the fact that for reaching a temperature decrease, the temperature of the cooling member must be lowered substantially below the desired cooling temperature.
The usual closed loop control of the temperature in cooling devices of known type occurs by switching the chiller on and off. In order to keep the life time of the chiller at an acceptable level, switching has to take place at comparatively large time intervals. This has the disadvantage that comparatively large temperature fluctuations are observed. In addition, it is disadvantageous that vibrations occur when switching on and off, which can affect the precision of the handling device.
Due to the heat generation of the handling device, the quality of the climate that can be achieved is impaired. Climate fluctuations and recovery times are substantial, in particular during a fast series of accesses. Devices of the above type are used in complicated and costly systems, into which they have to be integrated with a great effort. Their limited usability is therefore especially noticeable as a disadvantage. Because of the lacking versatility it is therefore necessary to use, depending on the application, several devices within one system.
Just as humidity, gases are reacting very strongly to access. Even if the access occurs through a comparatively small opening, its opening is connected to a distinct drop in gas concentration. The known devices for measuring gas concentration are arranged in the climate controlled chamber and have to withstand high humidity values. This substantially reduces the usability of sensors, and sensors must be used that have disadvantageous properties, such as low effective signals and drift.
Finally, the known devices are complicated to integrate into a host system because many functions must be implemented by the integrator and a plurality of interfaces are necessary, or certain functions cannot be carried out by the host system at all or certain values are not accessible for the same.